There are many applications which require parts to be detachably connected with a joint which is reliable, easy to operate, and holds the parts firmly together. Some applications in which such joints are desirable are in joining the components of a panel display system, in assembling modular kitchen cabinets and in assembling shelving units. Of course, many other applications are also possible.
For the purpose of illustration the novel joint of the invention is hereinafter described in the context of a panel display system. Such systems are frequently used for temporary displays in advertising, displaying information at conferences and the like. Ideally, a panel display system should be light in weight, inexpensive, quick and easy to assemble and should allow a wide variety of configurations to be constructed with a few basic components. A necessary prerequisite to making a panel display system with these attributes is a means for securely and easily detachably connecting the various components of the system together. It can be readily appreciated that a good attachment means for connecting the components of a panel display system will have application in many fields where it is desirable to quickly and securely detachably connect members together.
A typical panel display system includes a number of rigid members which can be connected to form a structure. Typically the structure is in the form of a framework with vertical members interlinked by a number of horizontal members. Connectors, which are usually integral with the ends of the horizontal members, are provided for joining the horizontal members to the vertical members. After the framework of vertical and horizontal members is erected, panels may be inserted in the rectangular spaces bordered by the members.
The difficulty with currently available panel display systems is that they use complicated means to connect the structural members. This makes these systems either expensive or time consuming to assemble or both. Similar problems exist in other fields in which detachable joints are used for linking parts together.
Staeger, U.S. Pat. No. 4,583,359 shows a modern system for assembling a display from portable frame members. The frame members are tubes with longitudinal undercut grooves on their exterior surfaces. The end of one tube can be clamped to a point along the length of a second tube by means of a clamping element which is affixed to the end of the first tube. The clamping element is inserted into one of the longitudinal grooves on the second tube and tightened by turning a screw. Turning the screw forces apart tie bar clamps at the end of the clamping element. As they are forced apart, the tie bar clamps are drawn toward the body of the clamping element. The tie bar clamps engage the undercut surfaces of the longitudinal grooves in the second member and hold the first member perpendicular to the second member.
The clamping mechanism described by Staeger has several parts and is therefore, relatively expensive to make. Furthermore, when the Staeger system is assembled, each joint must be individually tightened with a screwdriver. This makes assembly of the system relatively time consuming.
Chenel, U.S. Pat. No. 4,778,487 describes a modular panel display system of vertical and horizontal members which can be inter-connected to form a frame work. The vertical members have longitudinal T-shaped slots and the horizontal members have T-shaped bolts projecting from their ends. A horizontal member may be attached to a vertical member by aligning the bolt on an end of the horizontal member with the opening of the slot on the vertical member, inserting the bolt into the slot, and twisting the horizontal member about its axis. As the horizontal member is twisted the ends of the bolt engage in the T-shaped slot. The bolt is locked into place in the slot by a ball and spring detent mechanism. Chenel provides a further mechanical locking mechanism to lock the horizontal member at one of a number of particular positions along the vertical member. While the Chenel panel display system appears to be quick to assemble, it is relatively complicated and, therefore, expensive to manufacture.